Apparatus for purifying liquid by ultraviolet light irradiation

ABSTRACT

An apparatus for purifying liquid comprises a substantially tubular irradiation chamber ( 100 ) and a plurality of UV-LEDs ( 110 ) projecting ultraviolet radiation into it so as to irradiate the flow ( 106 ) of liquid being passed through it, where each of the UV-LEDs ( 110 ) is disposed upon the irradiation chamber ( 100 ) so that it is illuminated by at least one other of the plurality of UV-LEDs ( 110 ).

TECHNICAL FIELD

The invention relates to an apparatus for purifying water by ultravioletlight irradiation, as well as a dispensing apparatus comprising it.

BACKGROUND OF THE INVENTION

The present invention relates generally to an apparatus for purifyingwater, as well as to a beverage dispenser comprising it.

One of the most essential tasks in purifying liquids such as water fordrinking is disinfection, so as to ensure that any pathogenicmicroorganisms (e.g. bacteria, viruses, and protozoans) present in thewater cannot cause illness in anyone who drinks it. It is known toperform this disinfection by the process of ultraviolet (UV)irradiation, where a volume of water being treated is bombarded withhigh-energy radiation in the form of UV light. The UV light damages theDNA and RNA of the pathogenic microorganisms, destroying their abilityto reproduce and effectively neutralizing their ability to causedisease.

Since such systems use light to disinfect, their effectiveness isreduced on liquid which is not naturally clear or which has not beenfiltered to remove suspended solids. The scope of “purification,” forthe purposes of this document, should thus be understood as encompassingthe disinfection of liquid in which turbidity is minimal.

Traditional UV liquid purification systems have employed gas-dischargelamps as UV sources, in particular mercury-vapor lamps. Recently, it hasbecome more and more common to employ ultraviolet light-emitting diodes(UV-LEDs) as a source of ultraviolet light for irradiation. UV-LEDs havenumerous advantageous aspects which makes them appealing for use in anultraviolet liquid purification system, notably their compact size,robustness, and lack of toxic components such as the mercury vapor foundin conventional lamps. The solid-state nature of UV-LEDs also enablesthem to be switched on and off instantly, a further advantage relativeto conventional gas-discharge lamps.

It should be noted that, in this document, the term “ultravioletlight-emitting diode” is abbreviated to “UV-LED,” and that any incidenceof the latter term should not be interpreted otherwise.

However, unlike traditional gas-discharge lamps, UV-LEDs tend to emit UVradiation in a conical pattern with much less diffusion of the UV lightthan occurs with traditional gas-discharge lamps. Configuring a systemto use UV-LEDs will thus present a certain amount of difficulty, in thatthe emission pattern of UV-LEDs makes it much more difficult to properlyilluminate the entire volume of the irradiation chamber and achieve fullirradiation of the liquid therein, reducing the maximum flow rate ofliquid through the irradiation chamber.

There may thus be created so-called “dead zones” within the irradiationdevice which receive no significant ultraviolet irradiation. This, inturn, obligates the user to reduce the flow of liquid through theirradiation device, so that the entire volume of the flow is irradiatedto a sufficient degree.

There are certain systems known in the prior art which attempt toresolve this problem. The document KR 2010-0093259 describes a systemwhere arrays of UV-LEDs are disposed in tubes which extend through theirradiation chamber; this achieves sterilization of the water flowingthrough the irradiation chamber, but this system requires large numbersof UV-LEDs to be effective which makes it expensive to build and tooperate. The document WO 2012/078476 discloses a series of baffle-likereflectors which project from the sides of the irradiation chamber intothe flow of liquid and reflect the UV light into all parts of theirradiation chamber. Similarly, the document KR 2012-003719 discloses asterilizing apparatus where a rod-shaped light guide projects into anirradiation chamber and diffuses UV light therein from a source disposedoutside the chamber. These devices successfully direct the UV light intoall parts of the irradiation chamber, but their projecting naturedisrupts the flow of liquid, and their surfaces may become fouled withmineral and/or biological accretions, reducing the effectiveness of theapparatus and increasing the maintenance burden upon their users.

It is thus an object of the invention to provide a water purificationapparatus which resolves at least some of the foregoing problems.

SUMMARY OF THE INVENTION

According, therefore, to a first aspect, the invention is directedtowards an apparatus for purifying liquid, comprising a substantiallytubular irradiation chamber adapted to conduct a flow of liquidtherethrough, and a plurality of UV-LEDs disposed upon and configured toproject ultraviolet radiation into said irradiation chamber and therebyirradiate said flow of liquid.

According to the invention, the plurality of UV-LEDs is configured suchthat each of said UV-LEDs is directly illuminated by the ultravioletirradiation emitted by at least one other of said UV-LEDs.

In this way, the volume of the dead zones within the irradiation chamberwill be reduced or even eliminated. More specifically, since each UV-LEDemits ultraviolet irradiation in a conical pattern, disposing anyparticular UV-LED within the conical illumination pattern of at leastone other UV-LED means that the volume near, but not within, theillumination pattern of that UV-LED will be irradiated.

Moreover, disposing the UV-LEDs in this fashion will maximize the volumeof the irradiation chamber that is irradiated for any particular numberof UV-LEDs. A liquid purification apparatus configured according to thisaspect can therefore realize a maximum output for any given level ofpower consumption or vice-versa.

Preferably, the plurality of UV-LEDs are distributed along the length ofthe irradiation chamber with a substantially uniform linear spacing.

This is advantageous in that it maximizes the length of the portion ofthe irradiation chamber where the liquid therein is being irradiated. Assterilization effectiveness is partially a function of the irradiationtime, an apparatus so configured will extend the amount of time anyparticular unit volume of liquid flowing through the irradiation chamberwill be irradiated, thereby increasing the effectiveness of the liquidpurification apparatus. In this way, the flow rate through the apparatusmay be maximized without increasing its dimensions, number of UV-LEDs,or power consumption thereof.

Preferably, the plurality of UV-LEDs are distributed along the perimeterof the irradiation chamber with a substantially uniform angular spacingabout a longitudinal axis of said irradiation chamber.

This is advantageous in that the angle at which the ultravioletirradiation is directed into the volume of liquid will change as itflows through the irradiation chamber. This yields a thoroughirradiation throughout the volume of the liquid, without necessitatingthe flow of liquid locally churn, swirl, or otherwise flow in directionsnot parallel to the overall direction of flow. The overall efficiencyand effectiveness of the apparatus are thereby improved.

According to a preferred embodiment, each of said UV-LEDs is disposedupon the irradiation chamber directly opposite another of said UV-LEDs,thereby defining a plurality of UV-LED pairs.

This is particularly advantageous, in that the area surrounding each ofthe UV-LEDs will be irradiated with the strongest possible ultravioletillumination of the other UV-LED. Furthermore, the region of theirradiation chamber directly between them will be irradiated by bothUV-LEDs in the pair. The thoroughness of the purification of the liquidis thereby maximized.

Preferably, the UV-LED pairs are distributed along the length of theirradiation chamber with a substantially uniform linear spacing, andalong the perimeter of said irradiation chamber with a substantiallyuniform angular spacing about a longitudinal axis of said chamber.

In this way, the irradiation chamber will also realize the advantages asdescribed above in relation to the other embodiments of the invention.

In a practical embodiment, the distance along a wall of the irradiationchamber between any two adjacent UV-LEDs is less than or equal to twicethe width of the irradiation chamber multiplied by the tangent ofone-half the angle of emission of the UV-LEDs.

In this way, the illumination of each of the UV-LEDs is performed by atleast one adjacent UV-LED. The reliability of the apparatus is therebymaximized, since as at least some of the UV-LEDs will be illuminated bymultiple other UV-LEDs, the failure of a single UV-LED is less likely toresult in an insufficient irradiation of the flow of liquid.

Preferably, the irradiation chamber has a substantially constantcross-section.

This is advantageous in that since the geometric relations between theUV-LEDs, the flow of liquid, and the irradiation chamber are constantover the length of the irradiation chamber, the irradiation will be of asubstantially constant intensity. A substantially constant cross-sectionis also easier and less expensive to manufacture, such as by extrusionor other commonly-known techniques.

Preferably the cross-section is substantially circular.

This is particularly advantageous in that the cross-section of theirradiation chamber is symmetric and free from flat surfaces and sharpcorners which might disrupt the flow of the liquid through it.

In a practical embodiment, the UV-LEDs have an angle of emission equalto or greater than 90°.

This is advantageous in that with a wider angle of emission the UV-LEDsmay be placed on the irradiation chamber further apart from each otherwhile still realizing the requisite co-illumination. The construction ofthe irradiation chamber is thus simplified, and the apparatus comprisingit may be constructed at a lower cost.

Preferably, the angle of emission is between 110° and 130° inclusive,and preferably 120°.

An angle of emission in such a range is desirable in that it will createa broad cone of ultraviolet illumination within the irradiation chamber.This further ensures the elimination of dead zones within the volume ofthe irradiation chamber. UV-LEDs with emission angles around 120° arealso commonly available in commercial quantities and power outputs.

In a practical embodiment, at least part of an interior surface of theirradiation chamber is substantially reflective to ultravioletirradiation.

This ensures that the ultraviolet light emitted by the UV-LEDs is evenlydistributed about the irradiation chamber, bringing the volume of anydead zones down to an absolute minimum. The effectiveness of theirradiation chamber is thereby maximized.

Preferably, the interior surface of the irradiation chamber is at leastpartially coated in a substance which is substantially reflective toultraviolet irradiation.

This is particularly advantageous in that such coatings are easily andquickly applied, yielding a reflective layer that is consistent inthickness and reflectivity. This also enables the fabrication of theirradiation chamber in a material that is substantially transparent toultraviolet light (e.g. glass), the coating being removed from orotherwise not disposed thereupon at the locations where the UV-LEDsproject into the irradiation chamber. The construction of theirradiation chamber may thereby be made much more inexpensive, simple,and resistant to leakage.

In a preferred embodiment, the plurality of UV-LEDs are disposed upon anexterior surface of the irradiation chamber.

This is advantageous in that the UV-LEDs are disposed completely outsideof the flow of liquid through the irradiation chamber, and there are noopenings or other discontinuities in the irradiation chamber aside fromany inlet(s) and outlet(s). Furthermore, the disposition of the UV-LEDson an exterior surface of the irradiation chamber simplifies thepositioning of their electrical supply wiring, and facilitates anymaintenance that may need to be performed on the UV-LEDs.

According to a second aspect, the invention is directed towards abeverage dispensing apparatus comprising an apparatus for purifyingliquid as described above.

Such a beverage dispensing apparatus is advantageous in that it realizesin a practical application the advantages of the liquid purifyingapparatus as described above.

BRIEF DESCRIPTION OF THE FIGURES

FIGS. 1A and 1B are respectively longitudinal and lateral section viewsof an apparatus for purifying liquid, according to a first embodiment;

FIGS. 2A and 2B are respectively a side view and a lateral section viewof an apparatus for purifying water according to a second embodiment;and

FIGS. 3A and 3B are respectively a side view and a lateral section viewof an apparatus for purifying water according to a third embodiment.

DETAILED DESCRIPTION

For a complete understanding of the present invention and the advantagesthereof, reference is made to the following detailed description of theinvention.

It should be appreciated that various embodiments of the presentinvention can be combined with other embodiments of the invention andare merely illustrative of the specific ways to make and use theinvention and do not limit the scope of the invention when taken intoconsideration with the claims and the following detailed description.

Further, this document describes groups of components, which arereferenced with both a numeral and a letter, e.g. “widgets 10A, 10B, 10C. . . .” When such terminology is employed, it should be understood thatthe components in the group are substantially identical; that when theboth the numeral and letter are used it should be understood asreferencing individual members of the group, while when only the numeralis used it should be understood as referencing the group in itsentirety.

As used in this specification, the words “comprises”, “comprising”, andsimilar words, are not to be interpreted in an exclusive or exhaustivesense. In other words, they are intended to mean “including, but notlimited to.

Any reference to prior art documents in this specification is not to beconsidered an admission that such prior art is widely known or formspart of the common general knowledge in the field.

The invention is further described with reference to the followingexamples. It will be appreciated that the invention as claimed is notintended to be limited in any way by these examples.

The main principle of the invention is first described.

FIGS. 1A and 1B are respectively longitudinal and lateral section viewsof a device for purifying liquid. In FIG. 1A, the device is representedby the irradiation chamber 100, which is a substantially tubular,elongated structure having an inlet 102 and an outlet 104. The inlet 102is adapted to receive a flow 106 of liquid, which is conducted throughthe cavity 108 of the irradiation chamber and out the outlet 104.

While the flow 106 is in the cavity 108 of the irradiation chamber 100,it is irradiated with ultraviolet light emitted by the UV-LEDs 110. TheUV-LEDs are disposed upon an exterior surface 112 of the irradiationchamber 100, which is transparent to ultraviolet light where the UV-LEDs110 are disposed. The In this way, the flow 106 of liquid is irradiatedby each of the UV-LEDs 110 in turn, as it flows through the irradiationchamber 100.

Each of the UV-LEDs 110 emits ultraviolet light in a conical emissionpattern 114, which has its point at the UV-LED 110 and gradually expandsoutwards as it propagates across the cavity 108 of the irradiationchamber 100. In FIG. 1A, each of the emission patterns 114 is given adifferent cross-hatching, to illustrate their overlapping nature.

In this embodiment, the UV-LEDs 110 are disposed along the irradiationchamber 100 with a consistent linear spacing, such that as one movesalong the longitudinal axis 116 of the irradiation chamber 100,successive UV-LEDs 110 are separated by a distance 1/2s, with successiveUV-LEDs 110 on one side being thus separated by a distance of s. Thevalue of s is chosen as a function of the diameter of the irradiationchamber 110 and the angle of each emission cone 114 so that, as depictedhere, each emission cone extends to an edge of at least one of theUV-LEDs 110 opposite. In this way, any dead zone around the UV-LEDs isminimized.

In most embodiments, it will be advantageous to ensure that the internalsurface 118 of the irradiation chamber 100 is reflective to ultravioletlight. This will further serve to reduce, or even eliminate, any deadzones in the irradiation chamber 110, in that the portions of the volumeof the irradiation chamber 100 which are not directly illuminated by oneof the UV-LEDs 110 are irradiated by the reflected light.

In addition, this reflective property improves the sterilizationefficiency of the irradiation chamber 100, in that UV light which doesnot irradiate a pathogenic microorganism directly can still do so afterreflecting off of the interior surface 118 one or more times.

In practice, this reflective property can be achieved by the depositionof a coating 120 upon the interior surface 118 of the irradiationchamber 100, which is here only partially depicted in the interest ofclarity. This coating can be, for example, a layer of a polymer such aspolytetrafluoroethylene (PTFE), a metallic coating such as gold orsilver, or some combination of these or other appropriate substances.

The means by which this coating is applied will depend on theparticulars of the embodiment. For example, the irradiation chamber maybe provided as transparent glass, and the coating applied by vapordeposition upon the internal surface of the chamber.

FIG. 1B offers further illustration of this, in the form of the sectionA-A at the section line shown in FIG. 1A. Here, it can be seen that aflow (not shown) of fluid passing through the irradiation chamber 100will be irradiated throughout its section, as the UV-LEDs 110 illuminatethe entirety of its circular cross-section. Thus, even when the deadzones cannot be totally eliminated from the irradiation chamber 100, theflow of the liquid through the chamber will ensure complete irradiation.

FIG. 2A is a side view of an apparatus for purifying water according toa second embodiment. In this embodiment, the irradiation chamber 200 is,as in the previous embodiment, provided with an inlet 202 and an outlet204 adapted to conduct a flow 206 of liquid through the irradiationchamber 200. Ultraviolet radiation is projected into the cavity 208 ofthe irradiation chamber 200 by the UV-LEDs 210.

The UV-LEDs 210 are disposed upon the irradiation chamber 200 with asubstantially uniform spacing both in a linear sense along thelongitudinal axis 216, and in an axial sense about said longitudinalaxis 216. The UV-LEDs 210 are thus arranged upon the irradiation chamber200 in a helical arrangement that realizes the advantages describedabove.

FIG. 2B is a lateral section view of the irradiation chamber 200 throughthe section line B-B depicted in FIG. 3A. In FIG. 2B, it is seen thatthe angular spacing of the UV-LEDs 210 about the longitudinal axis 216(here designated by the symbol φ is substantially constant between eachof the UV-LEDs 210. This Figure also shows the wide-angled conicalemission patterns 214.

Thus, it can be seen that in any particular application, the propagationof the UV light within the irradiation chamber can be controlled bymodifying the parameters thus far described, including the angle of theemission patterns, the longitudinal spacing between UV-LEDs, the angularspacing of the UV-LEDs, the total active length of the irradiationchamber, and the number of the UV-LEDs.

The user can thus adapt the apparatus to the particular needs of theapplication for which it is destined; for instance, an application wherea high degree of sterilization is desired such as a dispenser for infantformula, can be provided with many UV-LEDs with tight linear and angularspacing, while other applications where the need for sterilization isnot so acute may be provided with fewer UV-LEDs and wider spacing.

FIGS. 3A and 3B are respectively a side view and lateral section view ofa liquid purifying apparatus according to a third embodiment. As in theprevious two embodiments discussed above, the apparatus comprises anirradiation chamber 300, provided with an inlet 302 and an outlet 304configured to direct a flow 306 of liquid through the cavity 308 of theirradiation chamber 300. The irradiation chamber is further providedwith a plurality of UV-LEDs 310, which project into the irradiationchamber 310 as in the two embodiments discussed above.

In this embodiment, the UV-LEDs 310 are arranged in pairs 350A, 350B,350C, and 350D. Each pair 350 is disposed so that the two UV-LEDsproject upon each other, such that they are at the same linear positionwith respect to the longitudinal axis 316, but have a 180° angularseparation about said longitudinal axis 316. The UV-LEDs 310 in each ofthe pairs 350 will thereby mutually illuminate each other, eliminatingany dead zone around them.

Furthermore, the pairs 350 of UV-LEDs 310 are disposed along the lengthof the irradiation chamber 300 with a substantially constant linearspacing, and about the longitudinal axis 316 of the irradiation chamber300 with a substantially constant axial spacing, substantially asdescribed in relation to the two previous embodiments. This spacingensures that the UV-LEDs 310 of each pair 350 are also illuminated by atleast one UV-LED 310 of another pair 350, in the same way as describedabove.

In this way, a thorough purification of the flow 306 of liquid isachieved. Moreover, because each UV-LED 310 is illuminated both by itscomplement UV-LED 310 in its own pair 350, and by a UV-LED 310 inanother one of the pairs 350, there is achieved a redundancy should oneof the UV-LEDs 310 fail. In this way, the reliability of the system isimproved.

FIG. 3B is a lateral section view of the irradiation chamber 300, takenat the section line C-C as depicted in FIG. 3A. Here, it can be seenthat the angular separation a between the UV-LEDs 310 of the pair 350Bis 180°; i.e. that the UV-LEDs 310 of the pair 350B are diametricallyopposed from one another. While not depicted for clarity, this angularrelation is the same for each of the other pairs 350A, 350D of UV-LEDs310.

Although the invention has been described by way of example, it shouldbe appreciated that variations and modifications may be made withoutdeparting from the scope of the invention as defined in the claims.Furthermore, where known equivalents exist to specific features, suchequivalents are incorporated as if specifically referred in thisspecification.

In a general sense, elements described in the foregoing disclosureshould not be taken as being limited to the combinations andconfigurations described in the foregoing example embodiments.Recombination of the elements described above according to theparticulars of each application should be considered as envisioned whennot in direct contradiction to this disclosure.

In particular, it should be recognized that, while the above embodimentsdescribe embodiments where there is a constant flow of liquid throughthe irradiation chamber, the invention is equally directed towardsembodiments where said flow is not constant, i.e. so-called “static”reactors. In such an embodiment, it may be that a volume of liquid flowsinto the irradiation chamber, is irradiated, and then subsequently flowsout. The foregoing disclosure should not, therefore, be construed asbeing limited to constant-flow apparatuses such as the embodimentsdiscussed above.

Also, while it is envisioned that an apparatus according to the presentinvention be integrated into a beverage dispensing apparatus, it mayequally be possible to employ such an apparatus in other applications,for example in commercial, industrial, medical, or other suchapplications where reliable purification of a liquid is sought. Inparticular, it may be advantageous to incorporate such an apparatus intodevices such as beverage vending machines, coffee or tea dispensers, ordispensers for prepared food such as soups, cereals, infant formula, orthe like.

It should thus be understood that various changes and modifications tothe presently preferred embodiments described herein will be apparent tothose skilled in the art. Such changes and modifications can be madewithout departing from the spirit and scope of the present invention andwithout diminishing its attendant advantages. It is therefore intendedthat the appended claims be considered as including any embodiment whichis derived at least partially from it.

1. An apparatus for purifying liquid, comprising a substantially tubularirradiation chamber adapted to conduct a flow of liquid therethrough,and a plurality of UV-LEDs disposed upon and configured to projectultraviolet radiation into the irradiation chamber and thereby irradiatethe flow of liquid, characterized in that the plurality of UV-LEDs areconfigured such that each of the UV-LEDs is directly illuminated by theultraviolet irradiation emitted by at least one other of the UV-LEDs. 2.The apparatus of claim 1, wherein the plurality of UV-LEDs aredistributed along a length of the irradiation chamber with asubstantially uniform linear spacing.
 3. The apparatus of claim 1,wherein the plurality of UV-LEDs are distributed along the perimeter ofthe irradiation chamber with a substantially uniform angular spacingabout a longitudinal axis of the irradiation chamber.
 4. The apparatusof claim 1, wherein each of the UV-LEDs is disposed upon the irradiationchamber directly opposite another of the UV-LEDs, thereby defining aplurality of UV-LED pairs.
 5. The apparatus of claim 4, wherein theUV-LED pairs are distributed along a length of the irradiation chamberwith a substantially uniform linear spacing, and along the perimeter ofthe irradiation chamber with a substantially uniform angular spacingabout a longitudinal axis of the irradiation chamber.
 6. The apparatusof claim 1, wherein the distance along a wall of the irradiation chamberbetween any two adjacent UV-LEDs is less than or equal to twice a widthof the irradiation chamber multiplied by the tangent of one-half theangle of emission of the UV-LEDs.
 7. The apparatus of claim 1, whereinthe irradiation chamber has a substantially constant cross-section. 8.The apparatus of claim 7, wherein the irradiation chamber has asubstantially circular cross-section.
 9. The apparatus of claim 1,wherein the UV-LEDs have an angle of emission equal to or greater than90°.
 10. The apparatus of claim 9, wherein the UV-LEDs have an angle ofemission between 110° and 130° inclusive.
 11. The apparatus of claim 1,wherein at least part of an interior surface of the irradiation chamberis substantially reflective to ultraviolet radiation.
 12. The apparatusof claim 1, wherein the interior surface of the irradiation chamber isat least partially coated in a substance which is substantiallyreflective to ultraviolet irradiation.
 13. The apparatus of claim 1,wherein the plurality of UV-LEDs are disposed upon an exterior surfaceof the irradiation chamber.
 14. A beverage dispensing apparatuscomprising an apparatus for purifying liquid comprising a substantiallytubular irradiation chamber adapted to conduct a flow of liquidtherethrough, and a plurality of UV-LEDs disposed upon and configured toproject ultraviolet radiation into the irradiation chamber and therebyirradiate the flow of liquid, the plurality of UV-LEDs are configuredsuch that each of the UV-LEDs is directly illuminated by the ultravioletirradiation emitted by at least one other of the UV-LEDs.